A common practice in forming fibers of mineral material is to pass the material in a molten state through the orifices of the peripheral wall of a centrifuge or spinner to create primary fibers. Thereafter, the primary fibers are further attenuated into a veil of secondary fibers of smaller diameter by the action of a flow of gases discharged downwardly. It is known in the prior art that the flow of gases can have high velocity in order to increase the air drag attenuation of the primary fibers into the secondary fibers. It is also known that the air drag attenuation provided to the primary fibers by the flow of gases can be greatly increased by creating some turbulence in the flow of gases.
One of the problems associated with fiber-forming apparatus of the prior art is that the blowers for secondary attenuation of the primary fibers into secondary fibers consume large amounts of energy. Another problem with the fiber-forming apparatus of the prior art is that limitations on the ability of the secondary attenuation function require that the primary fiber be sufficiently fine in diameter in order to result in an acceptably fine secondary fiber. For example, in order to form a secondary fiber within the range from about 4 to about 12 microns in diameter, it is necessary to produce a primary fiber having a diameter within the range of from about 15 to about 25 microns. The apparatus and method of this invention are directed towards the solution of the above problems.
According to this invention, there is provided apparatus for forming fibers comprising a spinner for centrifuging molten mineral material into primary fibers and a plurality of turbulent flow generators positioned circumferentially of the spinner to further attenuate the primary fibers into secondary fibers. The turbulent flow generators create turbulence sufficient to effect further attenuation of the fiber.
In one of its embodiments, the turbulent flow generators are vortex generators.
In another embodiment, the turbulent flow generators comprise two or more gas discharge conduits adapted to discharge gaseous flows which interact to form a vortex.
In another embodiment, adjacent vortices are counter-rotating.
In another embodiment, each of the turbulent flow generators comprises a gas discharge conduit adapted to discharge a gaseous flow, and a baffle positioned in the path of the gaseous flow, the baffle being adapted to increase the turbulence of the gaseous flow.
In another embodiment, the baffle is adapted to deflect the gaseous flow.
According to this invention, there is also provided apparatus for forming fibers comprising a spinner for centrifuging molten mineral material into primary fibers and a plurality of turbulent flow generators positioned circumferentially of the spinner to further attenuate the primary fibers into secondary fibers, each of the turbulent flow generators being adapted to generate gaseous flows exerting attenuating forces in different directions along the path of the fiber being further attenuated.
In one of its embodiments, the attenuation forces occur at spaced-apart loci within the turbulent flow.
According to this invention, there is also provided a method of forming fibers comprising centrifuging molten mineral material into primary fibers with a rotating spinner and further attenuating the primary fibers into secondary fibers by introducing the primary fibers into zones of turbulent gaseous flow, the zones being positioned circumferentially of the spinner. The zones have sufficient turbulence to effect further attenuation of the fiber.
According to this invention, there is also provided a method of forming fibers comprising centrifuging molten mineral material into primary fibers with a rotating spinner and further attenuating the primary fibers into secondary fibers by exerting attenuation forces in different directions at different loci within each of a plurality of zones of turbulent gaseous flow, the zones being positioned circumferentially of the spinner.
In one of its embodiments, vortices are generated to produce the attenuation forces.
In another of its embodiments, gas is discharged from two or more discharge conduits to generate each of the vortices.
In another of its embodiments, adjacent vortices are counter-rotating.
In yet another of its embodiments, gas is discharged from a gas discharge conduit and deflected with a baffle to generate the turbulent gaseous flow.
According to this invention, there is also provided the method of forming fibers comprising centrifuging molten mineral material into primary fibers with a spinner, generating a plurality of zones of turbulent gaseous flows positioned circumferentially of the spinner, each of the zones having gas flow in different directions at different loci within the zone, and further attenuating the primary fibers into secondary fibers by introducing the primary fibers into the zones.